/*
 * jcdctmgr.c
 *
 * Copyright (C) 1994-1995, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains the forward-DCT management logic.
 * This code selects a particular DCT implementation to be used,
 * and it performs related housekeeping chores including coefficient
 * quantization.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"
#include "jdct.h"				/* Private declarations for DCT subsystem */


/* Private subobject for this module */

typedef struct
{
	struct jpeg_forward_dct pub;	/* public fields */

	/* Pointer to the DCT routine actually in use */
	forward_DCT_method_ptr do_dct;

	/* The actual post-DCT divisors --- not identical to the quant table
	 * entries, because of scaling (especially for an unnormalized DCT).
	 * Each table is given in normal array order; note that this must
	 * be converted from the zigzag order of the quantization tables.
	 */
	DCTELEM        *divisors[NUM_QUANT_TBLS];

#ifdef DCT_FLOAT_SUPPORTED
	/* Same as above for the floating-point case. */
	float_DCT_method_ptr do_float_dct;
	FAST_FLOAT     *float_divisors[NUM_QUANT_TBLS];
#endif
} my_fdct_controller;

typedef my_fdct_controller *my_fdct_ptr;


/*
 * Initialize for a processing pass.
 * Verify that all referenced Q-tables are present, and set up
 * the divisor table for each one.
 * In the current implementation, DCT of all components is done during
 * the first pass, even if only some components will be output in the
 * first scan.  Hence all components should be examined here.
 */

METHODDEF void start_pass_fdctmgr(j_compress_ptr cinfo)
{
	my_fdct_ptr     fdct = (my_fdct_ptr) cinfo->fdct;
	int             ci, qtblno, i;
	jpeg_component_info *compptr;
	JQUANT_TBL     *qtbl;

#ifdef DCT_ISLOW_SUPPORTED
	DCTELEM        *dtbl;
#endif

	for(ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components; ci++, compptr++)
	{
		qtblno = compptr->quant_tbl_no;
		/* Make sure specified quantization table is present */
		if(qtblno < 0 || qtblno >= NUM_QUANT_TBLS || cinfo->quant_tbl_ptrs[qtblno] == NULL)
			ERREXIT1(cinfo, JERR_NO_QUANT_TABLE, qtblno);
		qtbl = cinfo->quant_tbl_ptrs[qtblno];
		/* Compute divisors for this quant table */
		/* We may do this more than once for same table, but it's not a big deal */
		switch (cinfo->dct_method)
		{
#ifdef DCT_ISLOW_SUPPORTED
			case JDCT_ISLOW:
				/* For LL&M IDCT method, divisors are equal to raw quantization
				 * coefficients multiplied by 8 (to counteract scaling).
				 */
				if(fdct->divisors[qtblno] == NULL)
				{
					fdct->divisors[qtblno] = (DCTELEM *)
						(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, DCTSIZE2 * SIZEOF(DCTELEM));
				}
				dtbl = fdct->divisors[qtblno];
				for(i = 0; i < DCTSIZE2; i++)
				{
					dtbl[i] = ((DCTELEM) qtbl->quantval[jpeg_zigzag_order[i]]) << 3;
				}
				break;
#endif
#ifdef DCT_IFAST_SUPPORTED
			case JDCT_IFAST:
			{
				/* For AA&N IDCT method, divisors are equal to quantization
				 * coefficients scaled by scalefactor[row]*scalefactor[col], where
				 *   scalefactor[0] = 1
				 *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
				 * We apply a further scale factor of 8.
				 */
#define CONST_BITS 14
				static const INT16 aanscales[DCTSIZE2] = {
					/* precomputed values scaled up by 14 bits: in natural order */
					16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
					22725, 31521, 29692, 26722, 22725, 17855, 12299, 6270,
					21407, 29692, 27969, 25172, 21407, 16819, 11585, 5906,
					19266, 26722, 25172, 22654, 19266, 15137, 10426, 5315,
					16384, 22725, 21407, 19266, 16384, 12873, 8867, 4520,
					12873, 17855, 16819, 15137, 12873, 10114, 6967, 3552,
					8867, 12299, 11585, 10426, 8867, 6967, 4799, 2446,
					4520, 6270, 5906, 5315, 4520, 3552, 2446, 1247
				};
				SHIFT_TEMPS if(fdct->divisors[qtblno] == NULL)
				{
					fdct->divisors[qtblno] = (DCTELEM *)
						(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, DCTSIZE2 * SIZEOF(DCTELEM));
				}
				dtbl = fdct->divisors[qtblno];
				for(i = 0; i < DCTSIZE2; i++)
				{
					dtbl[i] = (DCTELEM)
						DESCALE(MULTIPLY16V16((INT32) qtbl->quantval[jpeg_zigzag_order[i]],
											  (INT32) aanscales[i]), CONST_BITS - 3);
				}
			}
				break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
			case JDCT_FLOAT:
			{
				/* For float AA&N IDCT method, divisors are equal to quantization
				 * coefficients scaled by scalefactor[row]*scalefactor[col], where
				 *   scalefactor[0] = 1
				 *   scalefactor[k] = cos(k*PI/16) * sqrt(2)    for k=1..7
				 * We apply a further scale factor of 8.
				 * What's actually stored is 1/divisor so that the inner loop can
				 * use a multiplication rather than a division.
				 */
				FAST_FLOAT     *fdtbl;
				int             row, col;
				static const double aanscalefactor[DCTSIZE] = {
					1.0, 1.387039845, 1.306562965, 1.175875602,
					1.0, 0.785694958, 0.541196100, 0.275899379
				};

				if(fdct->float_divisors[qtblno] == NULL)
				{
					fdct->float_divisors[qtblno] = (FAST_FLOAT *)
						(*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, DCTSIZE2 * SIZEOF(FAST_FLOAT));
				}
				fdtbl = fdct->float_divisors[qtblno];
				i = 0;
				for(row = 0; row < DCTSIZE; row++)
				{
					for(col = 0; col < DCTSIZE; col++)
					{
						fdtbl[i] = (FAST_FLOAT)
							(1.0 / (((double)qtbl->quantval[jpeg_zigzag_order[i]] *
									 aanscalefactor[row] * aanscalefactor[col] * 8.0)));
						i++;
					}
				}
			}
				break;
#endif
			default:
				ERREXIT(cinfo, JERR_NOT_COMPILED);
				break;
		}
	}
}


/*
 * Perform forward DCT on one or more blocks of a component.
 *
 * The input samples are taken from the sample_data[] array starting at
 * position start_row/start_col, and moving to the right for any additional
 * blocks. The quantized coefficients are returned in coef_blocks[].
 */

#if 0							// bk001204
METHODDEF void
forward_DCT(j_compress_ptr cinfo, jpeg_component_info * compptr,
			JSAMPARRAY sample_data, JBLOCKROW coef_blocks, JDIMENSION start_row, JDIMENSION start_col, JDIMENSION num_blocks)
/* This version is used for integer DCT implementations. */
{
	/* This routine is heavily used, so it's worth coding it tightly. */
	my_fdct_ptr     fdct = (my_fdct_ptr) cinfo->fdct;
	forward_DCT_method_ptr do_dct = fdct->do_dct;
	DCTELEM        *divisors = fdct->divisors[compptr->quant_tbl_no];
	DCTELEM         workspace[DCTSIZE2];	/* work area for FDCT subroutine */
	JDIMENSION      bi;

	sample_data += start_row;	/* fold in the vertical offset once */

	for(bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE)
	{
		/* Load data into workspace, applying unsigned->signed conversion */
		{
			register DCTELEM *workspaceptr;
			register JSAMPROW elemptr;
			register int    elemr;

			workspaceptr = workspace;
			for(elemr = 0; elemr < DCTSIZE; elemr++)
			{
				elemptr = sample_data[elemr] + start_col;
#if DCTSIZE == 8				/* unroll the inner loop */
				*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
				*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
				*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
				*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
				*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
				*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
				*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
				*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
#else
				{
					register int    elemc;

					for(elemc = DCTSIZE; elemc > 0; elemc--)
					{
						*workspaceptr++ = GETJSAMPLE(*elemptr++) - CENTERJSAMPLE;
					}
				}
#endif
			}
		}

		/* Perform the DCT */
		(*do_dct) (workspace);

		/* Quantize/descale the coefficients, and store into coef_blocks[] */
		{
			register DCTELEM temp, qval;
			register int    i;
			register JCOEFPTR output_ptr = coef_blocks[bi];

			for(i = 0; i < DCTSIZE2; i++)
			{
				qval = divisors[i];
				temp = workspace[i];
				/* Divide the coefficient value by qval, ensuring proper rounding.
				 * Since C does not specify the direction of rounding for negative
				 * quotients, we have to force the dividend positive for portability.
				 *
				 * In most files, at least half of the output values will be zero
				 * (at default quantization settings, more like three-quarters...)
				 * so we should ensure that this case is fast.  On many machines,
				 * a comparison is enough cheaper than a divide to make a special test
				 * a win.  Since both inputs will be nonnegative, we need only test
				 * for a < b to discover whether a/b is 0.
				 * If your machine's division is fast enough, define FAST_DIVIDE.
				 */
#ifdef FAST_DIVIDE
#define DIVIDE_BY(a,b)	a /= b
#else
#define DIVIDE_BY(a,b)	if (a >= b) a /= b; else a = 0
#endif
				if(temp < 0)
				{
					temp = -temp;
					temp += qval >> 1;	/* for rounding */
					DIVIDE_BY(temp, qval);
					temp = -temp;
				}
				else
				{
					temp += qval >> 1;	/* for rounding */
					DIVIDE_BY(temp, qval);
				}
				output_ptr[i] = (JCOEF) temp;
			}
		}
	}
}
#endif							// 0

#ifdef DCT_FLOAT_SUPPORTED

METHODDEF void
forward_DCT_float(j_compress_ptr cinfo, jpeg_component_info * compptr,
				  JSAMPARRAY sample_data, JBLOCKROW coef_blocks,
				  JDIMENSION start_row, JDIMENSION start_col, JDIMENSION num_blocks)
/* This version is used for floating-point DCT implementations. */
{
	/* This routine is heavily used, so it's worth coding it tightly. */
	my_fdct_ptr     fdct = (my_fdct_ptr) cinfo->fdct;
	float_DCT_method_ptr do_dct = fdct->do_float_dct;
	FAST_FLOAT     *divisors = fdct->float_divisors[compptr->quant_tbl_no];
	FAST_FLOAT      workspace[DCTSIZE2];	/* work area for FDCT subroutine */
	JDIMENSION      bi;

	sample_data += start_row;	/* fold in the vertical offset once */

	for(bi = 0; bi < num_blocks; bi++, start_col += DCTSIZE)
	{
		/* Load data into workspace, applying unsigned->signed conversion */
		{
			register FAST_FLOAT *workspaceptr;
			register JSAMPROW elemptr;
			register int    elemr;

			workspaceptr = workspace;
			for(elemr = 0; elemr < DCTSIZE; elemr++)
			{
				elemptr = sample_data[elemr] + start_col;
#if DCTSIZE == 8				/* unroll the inner loop */
				*workspaceptr++ = (FAST_FLOAT) (GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
				*workspaceptr++ = (FAST_FLOAT) (GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
				*workspaceptr++ = (FAST_FLOAT) (GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
				*workspaceptr++ = (FAST_FLOAT) (GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
				*workspaceptr++ = (FAST_FLOAT) (GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
				*workspaceptr++ = (FAST_FLOAT) (GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
				*workspaceptr++ = (FAST_FLOAT) (GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
				*workspaceptr++ = (FAST_FLOAT) (GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
#else
				{
					register int    elemc;

					for(elemc = DCTSIZE; elemc > 0; elemc--)
					{
						*workspaceptr++ = (FAST_FLOAT) (GETJSAMPLE(*elemptr++) - CENTERJSAMPLE);
					}
				}
#endif
			}
		}

		/* Perform the DCT */
		(*do_dct) (workspace);

		/* Quantize/descale the coefficients, and store into coef_blocks[] */
		{
			register FAST_FLOAT temp;
			register int    i;
			register JCOEFPTR output_ptr = coef_blocks[bi];

			for(i = 0; i < DCTSIZE2; i++)
			{
				/* Apply the quantization and scaling factor */
				temp = workspace[i] * divisors[i];
				/* Round to nearest integer.
				 * Since C does not specify the direction of rounding for negative
				 * quotients, we have to force the dividend positive for portability.
				 * The maximum coefficient size is +-16K (for 12-bit data), so this
				 * code should work for either 16-bit or 32-bit ints.
				 */
				output_ptr[i] = (JCOEF) ((int)(temp + (FAST_FLOAT) 16384.5) - 16384);
			}
		}
	}
}

#endif							/* DCT_FLOAT_SUPPORTED */


/*
 * Initialize FDCT manager.
 */

GLOBAL void jinit_forward_dct(j_compress_ptr cinfo)
{
	my_fdct_ptr     fdct;
	int             i;

	fdct = (my_fdct_ptr) (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE, SIZEOF(my_fdct_controller));
	cinfo->fdct = (struct jpeg_forward_dct *)fdct;
	fdct->pub.start_pass = start_pass_fdctmgr;

	switch (cinfo->dct_method)
	{
#ifdef DCT_ISLOW_SUPPORTED
		case JDCT_ISLOW:
			fdct->pub.forward_DCT = forward_DCT;
			fdct->do_dct = jpeg_fdct_islow;
			break;
#endif
#ifdef DCT_IFAST_SUPPORTED
		case JDCT_IFAST:
			fdct->pub.forward_DCT = forward_DCT;
			fdct->do_dct = jpeg_fdct_ifast;
			break;
#endif
#ifdef DCT_FLOAT_SUPPORTED
		case JDCT_FLOAT:
			fdct->pub.forward_DCT = forward_DCT_float;
			fdct->do_float_dct = jpeg_fdct_float;
			break;
#endif
		default:
			ERREXIT(cinfo, JERR_NOT_COMPILED);
			break;
	}

	/* Mark divisor tables unallocated */
	for(i = 0; i < NUM_QUANT_TBLS; i++)
	{
		fdct->divisors[i] = NULL;
#ifdef DCT_FLOAT_SUPPORTED
		fdct->float_divisors[i] = NULL;
#endif
	}
}
